The autoantibody levels between these two sample handling methods were highly correlated, with a median correlation coefficient of 0.99 (0.91–1.00). Slopes of their linear regression curve across the 32 subjects were spread between

0.7 and 1.4. When correlations of protein concentrations from matched sets ZD1839 datasheet of samples across the 32 subjects were calculated between traditional and protocol handling methods, only 7 of the 12 biomarkers achieved correlation coefficients ≥ 0.95 with a range of 0.05 to 1.00 (Table 4). As shown in Fig. 1B, significant differences in biomarker concentrations, (>±15% median percent difference) between the two sample handling methods were seen in 67% (8/12) of the individual biomarkers measured. Of the markers with significant differences in the traditional samples, 7 biomarkers increased, while only leptin decreased. The EGF and IL-6 serum concentrations in samples handled with the traditional method increased as much as 40-fold, while VEGF-A and resistin concentrations also increased 2 to 4-fold. The MBDA scores were evaluated across different pre-analytical variables.

In Fig. 2A, a bias was observed when the difference of MBDA scores between plasma and serum was plotted against the MBDA scores of the serum samples. Samples with low serum MBDA scores had artificially inflated scores when plasma was used as a sample. While EPZ015666 changes in the concentration of several biomarkers were observed in this subset of samples, e.g., EGF, VEGF-A, resistin, the largest and most consistent change associated with the elevated MBDA score was reduced concentrations of EGF which has a negative coefficient in the algorithm. In Fig. 2B, a similar bias was observed when the difference of MBDA scores between the traditional vs. protocol serum sample handling methods was evaluated relative to the MBDA score for the protocol method. Again, samples

with low “protocol” MBDA scores were artificially inflated by the traditional method, but this time primarily as about a result of the elevated concentration of IL-6. In both comparisons, samples with artificially deflated scores were observed at high MBDA scores. While changes in several of the biomarkers were observed in the samples with the deflated MBDA scores, elevated EGF concentrations were consistently observed. This study investigated two types of pre-analytical variables that occur prior to the point of actual sample analysis: blood sampling methods (serum vs. plasma) and serum collection/handling methods (traditional vs. protocol). Although serum and plasma are both routinely collected samples and the composition is considered similar, this is the first study to the authors’ knowledge where quantitative measurements of 12 proteins in a multiplexed platform and eight autoantibodies from matched samples are compared in a systematic way in rheumatoid arthritis subjects.